Rotary hydraulic press



pril 25, 1961 D. cRoPP 2,980,960

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m w' ffm/P ffy Z1 fwd/@M United States Patent Oiice vROTARY HYDRAULICPRESS David Cropp, Warren, Pa., assigner to Warren Cornponents Divisionof El-Tronics, Inc., Philadelphia, Pa., `a corporation of PennsylvaniaFiled May 27, 19,57, ser. No. 661,959

7 claims. (cl. iis-2o) This invention relates to improvements in amachine for compression molding articles from various materials that areintroduced thereto in powdered, plastic, or pallet form. Moreparticularly, the invention deals with a rotary hydraulic press for usein the continuous molding of such articles. v

It is known that a variety of machines have heretofore been produced foruse in the continuous molding of articles and that such machines, to avarying extent, have served their intended purpose. However, in a rapidor high speed press, difficulty has always been encountered not only indesigning operative structure by which to obtain and accurately maintaintime sequences, but also in closing and opening the molding elements ofeach unit with necessary speed and accuracy, together with maintainingnecessary molding heat and pressure in order to assure exactduplication, one molded piece with respect to another. It is true thatsome currently manufactured molding machines are capable of high speedproduction, but objection is had to many of these machines by reason ofthe fact that the operation of closing and opening each molding unit isaccomplished entirely by mechanical means. Mechanical operation mayconstitute no serious objection in the molding of certain materials orin molding small parts of a simple nature. However, it is very oftennecessary to generate a high clamping force in a molding operation, andthe physical size of the units, to enable this in a Vmechanicallyoperated press, results in a bulky construction. Cost of materials andlabor, to say nothing of assembly, suggests that there is a limit beyondwhich it is impractical to produce presses in which high clamping forceis required. Furthermore, to maintain such units in proper cyclicaloperation with given pressure dur-ing each moldingperiod, a number ofoperative parts, embodied in each unit, must not only be accuratelyproduced and adjusted, but the parts of each unit must be continuallychecked by spot examination of the pieces as they are molded todetermine whether or not the operative parts of one or more of the unitshas become misaligned or misadjusted. Obviously, it is necessary thateither or both elements of a molding unit must be movable toward andaway from each other, but when the means by which these elements areoperated is entirely mechanical, the question o-f accuracy of alignmentof parts and maintenance of proper adjustment thereof becomes extremelyimportant. This is particularly true, of course, inthe high speedproduction of molded articles.

Generally, it is the object and purpose of the present invention toprovide a turret type molding machine in which many of the heretoforerequired operative mechanical parts commonly found necessary in theoperation of the elements of a molding unit are eliminated and thesubstitution for these parts of hydraulic means that is controlled byvalveswhich can be easily and accurately set with the expectation thatidentical mo-lded articles may be produced throughout long periods ofoperation and at a higher rate of production than would conceivably bepossible through use ofthe mechanical parts so replaced..

Specilically, the invention discloses a hydraulic press in which 'amultiplicityof identical molding units are radially arranged on arotatable turret. Each unit includes a pair of relatively movable moldmounting elements, one of the elements of each unit being supported by apiston enclosed within a cylinder, the piston being caused toreciprocate through admittance of fluid under pressure to one or theother'ends of the cylinder. The Huid serving to operate the elements ofsuch a unit is controlled by a selector valve. Multiplepassa'geways inthe selector valve are caused to register at predetermined stations,during complete rotation of the turret, to so admit and/or relieve fluidunder pressure as to cause the piston to separate the molding elementsfor the introduction of moldable material, or engage theseelermentsunder such pressure as may be required for the molding of anarticle. These stations take the form of cam plates which aresuccessively contacted by a cam lever extending from the selector valveof each unit. Since these plates are not only relatively yadjustabletoward or away from each other, but are also replaceable with plates ofdifferent contour, it follows that adjustment of one or both plates willalter the molding cycle. Also, replacement of a plate with another ofdiiferent contour may serve to change the time period required to soactuate the valve as to close or open a mold.

The present invention further proposes, in conjunction with the Vabovementioned valve controls, to eliminate the costly provision of heavyduty, high volume, pumping units by incorporating in one pumping system,high and low pressure means. To accomplish this, an accumulator tank isprovided wherein fluid is stored under pressure generally not in excessof two hundred and fifty (250) pounds. Fluid from this tank is utilizedto move the piston of a molding unit to an extent to bring the moldelements into close proximity. Essentially, a rather large volume o-ffluid is required to move each piston, but

the pressure of this fluid may be relatively low. How-f.

ever, to assure such pressure contact of the mold elements as toproperly compress the material to be molded, an additional force must beexerted, and such force is applied by a minute quantity of fluid from ahigh pressure line. The high pressure source of iluidis also connectedwith the other end of the cylinder through this valve and high pressureuid thus serves to move the piston in the opposite direction for thepurpose of separating the mold elements upon completion of a moldingoperation. Simultaneously with this separation of the molding elements,the valve enables return of fluid from beneath the piston to theaccumulator tank. Thus, the

' quantity of fluid required to move each piston in one direction isreturned to the tank and available to move the next piston when thevalve therefor has been actuated. Upon complete operation of a givenunit of the devices, a slight increase in fluid. bulk has been producedby reason of the small addition of uid from the high pressure line. Ifthis additional bulk was returned to the accumulator, the pressuretherein would increase beyond that desired and so, a valve in thisreturn line is provided which allows excess fluid to return to the mainstorage tank and thus limit not only the quantity of fluid but thepressure thereofin the accumulator tank.

Many additional objects and advantages of the in-l draulic turret pressin which one fornr of the invention' is embodied;

Fig. 2 isan enlarged fragmentary vertical View, partly `liatented Apr.25, 1961 in section, of one of the molding units, the supportingstructure therefor, and certain of the hydraulic connections to theunits;

Fig. 3 is an elevational view of one of the molding units and a portionof the supporting structure, being substantially identical, but on alarger scale, with the disclosure of such a unit in Fig. 2;

Fig. 4 is a front elevational view of the unit shown in Fig. 3;

Fig. 5 is a vertical sectional view of one of the units, being takensubstantially as suggested by the line 5-5 of Fig. 4, and shows oneextreme position of one of the mold elements and position of theselector valve therefor;

Fig. 6 is a view similar to Fig. 5, showing the other extreme positionof the same mold element, together with the changed position of theselector valve;

Fig. 7 is a greatly enlarged vertical sectional detailed view of theselector valve shown at the base of the unit in Fig. 5;

Fig. 8 is a horizontal view, partly in section, of the selector valve,being taken substantially as suggested by the line 8-8 of Fig. 4;

Fig. 9 is a vertical sectional View of the box in which a selector valveis mounted, this view showing all passageways entering and leaving thebox;

Fig. l is a vertical sectional view of the valve that is mounted in thebox shown in Fig. 9;

Fig. 11 is a View similar to Fig. 10 showing the valve in a ninetydegree rotated position with respect to that of Fig. l0;

Fig. 12 is a hydraulic diagram showing the position of the variouscontrol valves when the hydraulic uid has functioned to move the pistoninto the position shown in Fig.

Fig. 13 is another diagram showing the position of the valves when fluidhas moved the piston into the position shown in Fig. 6;

Fig. 14 is an enlarged vertical sectional view of the safety valveincorporated in the hydraulic circuit, the piston therein beingpositioned to permit iluid to ow from the accumulator to the lowpressure manifold (see Fig. 12);

Fig. 15 is a view similar to Fig. 14 and shows the piston in a positionto close off the accumulator and permit uid from the press to thestorage tank;

Fig. 15A is a side elevational view, partly in section, of the piston inthe safety valve shown in Fig. 14;

Fig. 15B is a horizontal sectional View, taken substantially on the lineISB-15B of Fig. 15A;

Figs. 16, 17, and 18 are identical fragmentary front elevational viewsof the selector valve showing two stages of operation thereof asrequired in the modified valve structure shown in Figs. 19 and 20;

Fig. 19 is a fragmentary vertical sectional view of a modification ofthe valve structure shown in Fig. 5;

Fig. 20 is a vertical sectional view, taken substantially on the line20-20 of Fig. 19 and shows the position of the valve parts when thecontrol lever is in the position shown in Fig. 16;

Fig. 2l is a view similar to Fig. 2O and shows the position of the valveparts when the control lever is in the position shown in Fig. 17; and

Fig. 22 is a view similar to Fig. 20, showing the position of the valveparts when the control lever is in the position shown in Fig. 18.

Referring more particularly to the drawings, the reference numeral isemployed to generally designate one form of a rotary turret press withwhich the presently disclosed invention is associated. The presscomprises two general parts; namely, a pedestal 11 and a rotatableturret 12. The press includes an upstanding center post 13 that issupported at its lower end upon the pedestal 11. Above the pedestal, asuitable hearing 14 and thrust bearing mount the base portion i@ 9i ill@turret 12 on the post. The turret base `16 mounts a ring gear 17. Ahousing 18, xed in any suitable manner to the pedestal 11, mounts avertical shaft 19, to the lower end of which is secured a large gear 21.Near its upper end, the shaft mounts a small gear 22 which meshes withthe ring gear 17. Any suitable means may be employed to drive the gear21, and through the small gear 22 and ring gear 17, the turret is causedto rotate about the post 13. Radially offset from the center post, theturret base 16 includes a circular upstanding support 23, the upper edgeof which terminates in a radially inwardly extendp ing annular shelf 24.Suitable vertical slots 26 are distributed about the support 23 for thepurpose of providing access to the molding units from the interior ofthe turret in order to provide rotatable hydraulic connections for eachunit. Further description will set forth the means by which iiuid from acommon pressure source and under two different pressures, may beselectively fed to the molding units at predetermined stations as theseunits move through a complete circle with the rotatable turret.

Mounted on and extending radially outwardly of the shelf 24 are aplurality of individual uprights 27. They are uniformly distributedvabout the turret and are of a number corresponding to the number ofmolding units on the press. Although the structural and operationaldetails of only one molding unit will be specifically described, it willbe understood that all of the units of the press are identical and aresequentially operated in the manner hereinafter set out. Integral withand extending radially outwardly from the vertical reinforced portion 28of each upright are housings 29 and 30 which serve to mount and guidethe relatively movable elements of a mold. The upper housing 29 isintended to carry a receiver 32 that in turn mounts the upper element 33of a mold. This element is connected, as suggested in the drawings, witha suitable source of current supply which, in conventional manner, isautomatically controlled to provide required molding heat. The lowerhousing 30 has a vertical opening 31 to receive a shaft 34. At the upperend of this shaft is a seat 36 on which is located a receiver 37 for thelower element 38 of the mold. This element is also connected with asource of current supply, the heat thereof being automaticallycontrolled. At the point of entry of the shaft 34 into the housing 30,the housing opening is enlarged to receive packing 39 which may be heldin place lby a collar 41. The shaft 34 is of a length to at all timesextend completely through the housing 30, the lower end thereof takingthe form of a pin 42 to which is attached a head 43. This head is of thenature of a piston head and includes a series of annular grooves inwhich sealing rings 44 are located.

A series of rods 46 depend from the housing 30 and, at their lower ends,engage and Support a selector lvalve box 47. 'In the top, iiat face ofthis box is a cylindrical recess 48 (see Fig. 7) which receives andrfluid seals the lower end of a sleeve 49. The upper end of this sleevehas 'fluid sealing engagement with the walls of a recess 50 in the lowerface of the housing 29 (see Figs. 5, 6, and 7).. This sleeve is centeredwith the shaft 34 and serves as a cylinder within which the piston head43 is movable. A small horizontal opening 51 is made in the lower end ofthe housing 30 and opens into a small offset 52 of the opening throughwhich the shaft 34 projects. Extending upwardly from the bottom of thishousing is a further opening 53 which connects with the opening 51. Aplug 54 closes the exterior end of the opening 51 and these openingsthus provide for fluid passage between the exterior and the upperinterior end of the sleeve 49. A tube 56 is connected with the opening53 of the housing 30 at one'end and at its other end extends into thetop of the box 47 For convenience of operation and location, eachselector valve box 47 is arranged with its moving parts operable about ahorizontal axis. The box is formed with a generally centeredcylindrical, horizontal opening 57 extending from one end to the other.fIn the top of this opening, a passageway 58 connects with the tube 56.Also, there is a passageway 59 that connects the opening 57 with therecess 48, the base of which constitutes the lower end of the cylinder49. lConnecting the base exterior of the box with the opening 57 arethree passage- Ways; namely, 61, 62, `and 63. P'assageway 61 is adjacentone end of the box and more nearly centered is passageway 62 which has areduced diameter orifice 64. Passageway 63 is of considerably largerproportions and opens into a check valve 66, built into the base of thebox, as well as into the opening 57. From this valve an opening 67 ismade upwardly through the box, adjacent to but not connected withopening 57, Iand this opening 67 connects the check val've with theinterior of the cylinder in the 4recess 48. It is the purpose of thecheck valve 66 to permit fluid flow from the passageway 63 into the baseof the cylinder through opening 67 but prevent return of Huid throughsaid opening into passageway 63.

Mounted in the opening 57 and extending the full length of the box 47,is -a'shaft 68. shaft is of reduced diameter and extends beyond the boxand is fitted with a crank arm 71, the yfree end of which mounts aroller 72. Since the shaft is of the nature of a rotatable valve andmust be fluid tight, suitable packing glands encircle it, being carriedby the walls of the opening 57. The ends of the shaft are suitablysealed against fluid leakage and held in place by end plates 74, the endplate adjacent the crank serving as a spacer therefor. The shaft 68 hasa series of four passageways extending diametrically therethrough. Twoof the passageways are at right angles to the other two passageways.Considering Fig. 5 or 7 for the moment, in conjunction with Figs. 9 andl0, it wil be noted that with the crank arm 71 in its lowermostposition, an inclined passageway 76 connects the reduced orificepassageway 62 with the tube 56 through passageway 58. A further inclinedpassageway 77 connects the large passageway 63 with the passageway 59opening into the base of the cyhnder 49. Referring now to Fig. 6, inconjunction with Figs. 9 and 11, it will 'be noted that when the crankarm 71 has been rotated upwardly ninety degrees, the other twopassageways in the shaft 6'8 come into use; that is, passageway 78 nowconnects passageway 61 with the tube 56 and a small inclined passageway79 now connects the reduced orifice passageway 62 with the passageway 59that leads into the base of the cylinder 49. Of course, when passageways78 and 79 are in position of use, passageways 76 and 77 are closed, andvice versa. lOne end of a tube 81 is connected with the base of thevalve box 47 at the passageway 63. The other end of this tube is joined4 to a manifold l82 that encircles the turret 12 land rotates therewith.A further tube 83 connects passageway 62 with another manifold 84 whichis also carried by and rotatable with the turret 12. The exterior end ofthe passageway 61 is coupled through a tube 86 with a further manifold87 carried by the turret.

It is the purpose of the crank arm 71 to rotate the vvalve `shaft 68ninety degrees rst in one direction and then in the other. To accomplishthis, two cam plates 88 and 89 `are supported in any suitable manner onthe base of the press. Cam plate 88 is so designed that when a crankroller 72 contacts it, the roller will move up the inclined surface androtate the crank arm nlnety, degrees. Such rotation of the crank armchanges the position of the passageways in theselector valve box fromthat of Fig. 5 to that of Fig. 6 (see also Figs. 10 and l1.respectively). Cam plate 89 is reversely positioned to plate 88 and isintended to be contacted by roller 72 when the crank arm 71 is in raisedposition and, by moving the roller downwardly of the inclined surface,this arm is'rotated ninety degrees in the opposite direction, returningthe position of the passageways in the valve box to that of Fig. 5.

One end 69 of this There are only two fluid connections leading to theturret supporting post 13; namely, ia high pressure line and a returnline. These'lines extend upwardly through the post and terminate incollector rings 91 :and 92 which are shown in Fig. 2 and indicated inthe diagrams of Figs. 12 and 13. Ring 91'provides fluid take-off fromthe high pressure line Iand ring 92 for return of fluid to the postreturn line. The means by which it is possible to pass fluid fromstationary lines to rotating lines, such as are provided in the turret12, may be accomplished in any of several ways and, since this structureforms no part of the present invention, it is not shown or described indetail. As will hereinafter be clearly set out, the high pressure ring91 is connected wit-h the manifold `84 and the ring 92 is connectedwithv manifold 87. The further manifold y82 has connection with a sourceof vfluid that is under a pres-sure of less value than that supplied tothe high pressure manifold 84. To obtain fluid pressures of twodifferent values, an accumulator tank is provided and in order toadequately protect the operative parts of the units, a safety valve ofparticular structure and operation is installed in the system.

Attention is now particularly -directed to the operation of each of themolding units and the means by which it is possible to quickly,laccurately, and easily lopen and close them through the use of lasingle iiuid pressure line and a fluid return line. Referring moreparticularly to Figs. 5 through 8, it is to be observed that eachmolding unit, at the base thereof, has a selector valve 47 and that thepassageways to this Valve tare joined by fluid carrying tubes with thethree manifolds, 82, 84, 4and 87. In other Words, the number of moldingunits that may be mounted on the turret is limited only to the lateralproportions of each unit inasmuch -as control, by way of the selectorvalves, is made possible by Ithe circular manifolds which may be tappedat any point as required. It is to be particularly noted that since theselector valve 47 of each molding unit is individually operated by camplates 88 and 89, it is unnecessary to pro-vide an equivalent number ofthigh, low, and return fluid lines due to the manifold-s 82, 84, and 87.In other words, a single high pressure line, connected with la pump,will feed high pressure into manifold 84 .and at such time las theselector valve of a given unit is operated, high pressure iluid will beutilized in the opening or closing of -a given molding unit. Similarly,there is only a single return line to the fluid storage tank of the pumpthat is connected with the return manifold 87 and, consequently, all uidto be returned to the tank flows into this single line through thecollector ring 92 Iand back to the tank.

Referring now to Fig. 2 and the diagrams of Figs. l2 and 13, it will benoted that between the collector rings 91 and 92 mounted on the post 13and the three manifolds 82, 84 and 87, a safety valve and an accumulatoror low pressure ltank are located. The safety valve, indicated `at 93,serves Ito prevent the closing of any molds that may be open if, lforany reason, pressure from the fluid pump should drop below a certainvalue while the accumulator is still capable of delivering uid underpressure. Thus, this valve is interposed between the accumulator and thelow pressure manifold 82. More specifically, this valve consists of asleeve 94 that is closed `at its ends by Vsuitably attached-plugs 95 and96. A relatively smal-l opening 97 extends through the plug 96. Threadedinto the outer end of this opening is the stem of a three-way coupling98. This coupling is in the high pressure line 99 that connects themanifold 84 with the collector ring 91 Iand permits entry of highpressure fluid to this end of the valve. Three openings are vmade in thesleeve 94. Opening 100, through tube 101, is directly connected tomanifold 82. Diametrically opposite opening 100 are openings 102 and103. A tube 104 connects opening 102 with the accumulator tank 105. Afurther tube 106 connects opening 103 with =a return tube 107. This lasttube connects the ret-urn manifold S7 with the -return collector ring92. Either in the line between the tank 105 and valve 93, for built intothe tank, is a pressure relief valve 108, which is so designed thatfluid pressure beyond its set value cannot enter the tank 105 but mustby-pass through a tube 109 into the return collector ring 92. Within thesleeve 94 is a free piston '110. From one end of this piston, a stem 111extends into the opening 97, being provided with suitable packing bywhich to prevent entrance of fluid into the sleeve from the highpressure line 99.

The piston 110, as shown in Fig. 15A, has annular grooves at its ends inwhich suitable packing 112 is mounted. Between these packings are aseries of radially outwardly opening lengthwise grooves 113. Thesegrooves, when the piston is in one or the other of the positions shownin Figs. 14 and 15, connects the openings 100, 102, and 103 in apredetermined manner. During normal operation of the press, fluid in thehigh pressure line 99 acts upon the stem 111 to force the piston 1110into the position shown in Fig. 14 and to so maintain it as long as highpressure is available. In this position, the piston grooves 113 providefluid connection between openings 102 and 100, thus, through tubes 104and 101 fluid under low pressure from the accumulator 105 is madeavailable to the manifold S2. However, should the pressure in line 99drop below the pressure maintained in the accumulator 105, the pistonwill move into the position shown in Fig. l5. In this instance, fluid inthe press will be permitted to pass through the valve 93 from opening100 to opening 103 and thence, by way of tubes 106 and 107, lto thereturn collector ring 92.

As has already been stated, the present invention is particularlydirected to means for controlling the sequential operation of themolding units of a press by hydraulic pressures of two different values.To enable a full and clear understanding of the invention, attention isnow directed to Figs. 9, 10, and 11 and the diagrams of Figs. l2 and 13in connection with operation of the press. Although operation of onlyone molding unit will be described in detail, it will be obvious thatthe remaining molding units in the press will operate in like manner asthe control crank arms 71 are sequentially moved by reason of therollers 72 thereof coming in contact with cam plates 88 and 89. It willbe assumed that the fluid pump has been set in operation and that fluidunder high pressure is supplied to the line 114 that leads upwardlythrough the hollow post 13 into the collector ring 91 and supplies fluidto the manifold 84. With the crank arm in the position shown in Figs. 5,7, and l0, it will be noted that fluid from the pump flows throughpassageway 76, tube 56, and exerts a downward force on the piston 43 forthe purpose of holding the elements of the mold in separated or openedposition.

As a given molding unit reaches the point where the roller 72 contactsplate 88, the arm 71 of this unit is rotated from the position shown inFig. 5 or l0 to that of Fig. 6 or l1, thus causing the valve shaft 68 torotate ninety degrees and change the position of the passagewaystherein. In this position of the shaft, passageway 63 is blocked orclosed by a solid portion of the shaft. However, low pressure fluid intube 81 will pass through check valve 66 and opening 67 directly intothe base of the cylinder 49, thus exerting a force against the underface of the head 43. Passageway 79 of the shaft 68 now connects thereduced orifice passageway 62, with opening 59 in the base of thecylinder 49. Passageway 62, being connected with the manifold 84, nowpermits restricted flow of high pressure fluid from the pump into thecylinder 49 beneath the head 43. In other words, the mold is caused toclose through the application of a large volume of low pressure fluid,aided by a restricted amount of high pressure fluid. As a result of thisrotation of the shaft 68, the passageway 78 connects tube 56, throughpassageway 58, with the return line 86 that is joined to the returnmanifold 87. Thus, as fluid under both high and low pressure forces thepiston upwardly, fluid above the piston is enabled to return, throughmanifold 87, tube 107, collector ring 92, to the line 115 in the postwhich opens into the fluid reservoir. Inasmuch as cam plate 89, whichserves to rotate the arm 71 to open a molding unit, is adjacent the camplate 38 by which the unit is closed, it is evident that the turretmakes almost a complete rotation between mold closing and mold openingpositions. Consequently, molding material supplied to a given unit isheld under pressure throughout the time it takes the press to revolvebetween these two points and, of course, the elements of each moldingunit being electrically heated, the material will be properly processedby heat and pressure by the time the elements of the mold are againopened.

The return of the arm 71 of a unit to the position of Fig. 5 or l0causes the selector valve shaft 68 to again connect the passageways andfluid tubes in the relationship described when a given unit is at rest.It has been stated that operation of each molding unit is obtainedthrough use of fluid under relatively high and low pressure, althoughonly a single high pressure fluid line enters the press. Attention isparticularly directed to Figs. 5 and 7 and diagram 13. Herein highpressure fluid, applied to the top of the piston 43, through tube 56,has forced the piston downwardly in the cylinder 49 against low pressurefluid therebeneath. Of course, the fluid beneath the piston must beevacuated, and such evacuation occurs by this fluid flowing through thelarge passageway 77 of the selector valve, tube 81, manifold 82, andtube 101 into the safety valve 93. Since the pressure in line 99 isholding the safety valve piston 110 in the position shown in Fig. 14,fluid will flow freely through valve 93 from tube 101 to tube 104 andthence into the accumulator tank 105. The cubic capacity of theaccumulator tank 105 is greater than the cubic content of the cylinder49 when the piston is in raised position. Thus, the closing and openingof one molding unit will not lill the accumulator with fluid underdesired pressure. However, the subsequent sequential closing and openingof only a few of the molding units will build up the desired operativepressure in the accumulator. It will be understood that the fluidentering the press may do so under pressure of many hundred pounds,whereas pressure in the accumulator, which is the source of low pressurein the device, would preferably not exceed two hundred and fifty (250)pounds. The relief valve 10S, at the entrance to the accumulator, has avalue such that when pressure in the accumulator reaches a predeterminedpoint, the valve opens and by-passes excess fluid through the returnlines 109 and 107, to the collector ring 92, and thence out of the pressthrough tube 115.

Now that the press contains adequate fluid under a controlled lowpressure in the accumulator, molding may take place. When the crank arm71 has moved upwardly, fluid in considerable volume, at low pressure,from the accumulator 105, flows through the safety valve 93, manifold82, and into and through the one-way check valve 66, from which itenters the cylinder beneath the piston 43. Simultaneously with this lowpressure flow, passageway 79 of the selector valve has been opened andthus high pressure, through the flow restricting valve 64, also entersthe cylinder beneath the piston. It is not only contemplated, but inactual productive operation it has been proven, that through the use offluid under low pressure automatically provided in the press, it is onlynecessary to supply a small volume of fluid under high pressure not onlyto raise the piston and close the molding elements, but to hold theseelements in desired pressure engagement for a given molding operation.In this way, each press, in which the invention is utilized, need onlybe provided with a fluid pumping unit capable of producing a minimumquantity of fluid under high pressure, and it has been found that aconsiderable econline from the accumulator.

omy is effected through the use of smaller pumping equipment, smallerfluid reservoir, and also by reason of the elimination of all but twolines; one into and the other out of the press.

-Fluid under llow pressure from the accumulator serves only to raise thepiston 43 and may not completely close the molding elements or hold themin desired pressure contact through a molding operation. However, uidfrom the high pressure line, through passageway 79 and ow restrictingvalve 64, supplies iluid for this purpose. Consequently, whenV thepiston has reached its uppermost position there is more Huid beneath thehead 43 than entered the cylinder 49 by way of the low pressure Thus,when the mold is caused to open by reason of supplying fluid under highpressure to the top top of the piston, the fluid provided from theaccumulator has been increased in volume to the extent of flow from thehigh pressure line during raising the piston. And, of course, thepressure of 'this uid is greater than that required or supplied by theaccumulator. .In this conenction, it will be noted that the passageways59, 77, and 63 (see Figs. 9 and l0) are relatively large and thus themoment the piston is forced downwardly, fluid therebeneath is free topass through the manifold 82, tube 101, safety valve 93, and into theaccumulator. Ashas been mentioned, if the pressure of this return of uidis greater than the value set for the accumulator, and because morefluid is available to the accumulator than previously, the relief Valvewill function to by-pass this excess fluid, returning it to the tank ofreservoir of the pumping unit.

It is to be understood that during operation of the press there is noperiod when uid, under low pressure, is not applied to the cylinder 49beneath the piston 43. In other words, it is the difference in force asbetween the accumulator and the high pressure line, that causes downwardmovement of the piston, or, when high pressure is cut off, enablesupward piston movement. This constant availability of fluid under lowpressure to the units is to 'be kept in mind not only in connection withthe provision of a safeguard to withhold this lluid but also withrespect to a modification of the invention as hereinafter set out.

Following a period of operation of the press, the fluid pressure pumpand the turret drive may be shut oi. Obviously, the elements of a numberof molding units will be in open position at the time of such shut-down,at least as many as are between the cam plates 88 and 89. Now, therewould be no pressure in line 99 and, even though certain crank arms 71are in their lowered position, no fluid pressure would be applied to thetop of the pistons 43. However, with the selector valve in a position toseparate the mold elements, passageway 77 of shaft 68 still connectspassageway 63 with 59 which opens into the base of the cylinder 49. And,of course, passageway 63 connects through tube 81, manifold 82, tube101, safety valve 93, and tube 104 with the accumulator. Since thepressure in the accumulator tank has not been relieved, fluid thereinwould ow through the passageway 77, raise the piston 43 and at leastpartially close the mold of one or more of the units, this in spite ofthe fact that the have been stopped. With any of the movable elements ofthe units partially raised in "that area between cams 8S and 89, it isconceivable that the material feeding mechanism for the molding unitswould be interfered with when these partially or fully closed units werei presented to it at the time of again starting operation of the press.Also, lat the time of a shut-down of the press for repairs orexamniation, it would be unsafe to continue 'the availability of uidunder pressure even though the` pressure is low and only supplied fromthe accumulator tank. The safety valve 93 overcomes this hazard.

As has been previously stated, the safety valve piston 1,10 is held inthe position shown in Fig. 14 only so long press and the fluidpressurepump as there is fluid under high pressure in the incoming line99. As soon as this pressure drops, the piston 110 is forced into theposition shown in Fig. 15, by reason of fluid pressure from theaccumulator. This, of course, closes the opening in the valve to tube164 leading to the accumulator and opens the valve to the return line106. This adjustment of the valve serves two purposes; (1) to preventuid under pressure in the accumulator from raising any of the pistons43; and (2.) permits releasing pressure of any fluid vbeneath thepistons into the return line. Since pressure from the accumulator isshut off, and pressure both above and below the piston 43 is relieved,there can be no indavertent movement of parts when an operator shutsdown the press. Of course, when the press is again put into operation,fluid under pressure in the line 99 will move the piston 110 to theposition in Fig. 14 and again permit ow of fluid to and from theaccumulator tank through the safety lvalve 93.

In the compression molding of certain articles or of articles fromcertain materials, it is sometimes desirable, or even necessary, tobring together the elements of a mold under a low clamping force. Thisserves to delay, from the time of `filling a mold cavity, the moment atwhich the mold elements are subjected to full molding pressure. Ineffect, this provides a relatively short period in which the material ispre-warmed or heated and, of

course, this period must be variable. Attention is now directed to amodification of the invention shown in Pigs. 16 to 22 of the drawings.In Figs. 16, 17, and 18, an exterior portion of the base of a moldingunit is shown. In Fig. 16, the crank arm 71 occupies the same positionas it does in lFigs. 2, 5, and 7. The roller 72 of this arm is intendedto have a two-stage movement into its uppermost position, shown in Fig.18, which is similar to Figs. 6, 8, and 1l. Herein, a cam plate 116,shown in dash line, is substituted for the plate 8S and has a firstincline 117, a at step 118, and a second incline 119. Thus, as theturret revolves, the selector valve, by means of the arm 71, is turnedas a first step to a forty-five degree extent and, following a shortdistance of rotation of the turret, the arm 71 rotates the selectorvalve a full ninety degrees. It is with this step rotation that thismodification is particularly concerned, and attention is now directed toFig. 20.

With one exception, the shaft 68 of the selector valve is identical withthe shaft previously described. This exception has to do with thepassage of iluid through tube 56 to the return line 86. In thismodification, a passageway is substituted for the passageway 78previously described. The passageway 120, at its ends, is of enlargedproportions to create pockets 121 which extend circumferentially of theshaft in opposite directions in the manner and substantially to theextent shown in the drawings. As may be seen in Figs. 19 and 20,passageway 120 is at right angles to passageways 58 and 61 and, thus,with the arm 71 in its lowermost position, there can be no low of huidfrom the top of the piston to the return line S6. However, as the roller72 rides up the incline 117 of cam plate 116 and onto the ilat step 118,the shaft 68 of the selector valve has rotated from the position shownin Fig. 16 to that of Fig. 17. In this latter figure (see also Fig. 2l)it will b e apparent that the beginnings of the pockets 121 registerwith passageways 58 and 61. Thus, although fluid from the high pressureline 83 has not yet been admitted to the cylinder 49 beneath the piston43, pressure of uid above the piston is now relieved and may commenceflowing back into the return line 107. It will be recalled that at alltimes during operation of the press, low pressure fluid from theaccumulator is connected with the cylinder 49 beneath the piston 43.Consequently, when high pressure above the piston is thus relieved, low

pressure will force the piston upwardly and bring the l elements of amold into close proximity. The length of step 118 determines the lengthof time the mold elements are held closed under low pressure and, ofcourse, this time period may be increased or decreased by changing thelength of the step. When the crank 71 moves up the further incline 119to the position shown in Fig. 18, the selector valve shaft 625 will haverotated ninety degrees, with the passageway 12) remaining open. However,at this point, fluid from the high pressure line is now admitted to thecylinder 49 through passageway 79. The cam plate that serves to move thecrank arm 71 into its lowermost position is the same as cam 89 alreadydescribed. During this direction of rotation of the valve shaft 65, itis unimportant that the passageway 120 does not close immediately,inasmuch as it is only necessary to be fully closed by the time thepassageways 76 and 77 register with their respective openings orpassageways in the valve box.

Although applicant has shown and described only one form of hisinvention, together with a modification in the selector valve forpreliminary relief of fluid pressure on the piston head of each moldingunit, it will be understood that variations of the structure shown anddescribed may be made and are contemplated insofar as such variationsare within the spirit and scope of the annexed claims.

Having thus set forth my invention, what I claim as new and for which Idesire protection by Letters Patent is:

l. In a molding machine having a rotatable turret, a plurality ofmolding units disposed radially about said turret, hydraulicallyoperated mechanism for closing and opening the molding elements of eachof said units, an external source of high pressure fluid entering saidturret, an accumulator in said turret providing fluid under lowpressure, a cylinder having a piston therein joined to one of theelements of each of said units, a valve for each of said unitsinterposed between said cylinder and lines from said high pressuresource and said accumulator, said valve having two sets of passageways,one of said sets being connected with said cylinder, the other of saidsets being connected with said sources of fluid under high and lowpressure, a rotatable shaft in said valve, further passageways in saidshaft, said shaft being rotatable to connect certain passageways of saidsets whereby to selectively present high pressure fluid to the top andbottom of said piston and to at all times present low pressure fluid tothe bottom of said piston during operation of said machine.

2. In a molding machine having a rotatable turret, a plurality ofmolding units disposed radially about said turret, hydraulicallyoperated mechanism for closing and opening the molding elements of eachof Said units, an external source of high pressure fluid entering saidturret, an accumulator in said turret providing fluid under lowpressure, a cylinder having a piston therein joined to one of theelements of each of said units, a valve for each of said unitsinterposed between said cylinder and lines from said high pressuresource and said accumulator, said valve having two sets of passageways,one of said sets being being connected with said cylinder, the other ofsaid sets being connected with said sources of fluid under high and lowpressure, a rotatable shaft in said valve, further passageways in saidshaft, said shaft being rotatable to connect certain passageways of saidsets whereby to selectively present high pressure fluid to the top andbottom of said piston and to at all times present low pressure fluid tothe bottom of said piston during operation of said machine, and a safetyvalve consisting of a cylinder and a piston therein, connection of saidhigh pressure fluid with said cylinder serving to hold said piston in aposition to permit low pressure fluid from said accumulator to passthrough said safety valve to the rst mentioned cylinder when said highpressure fluid is above a given value.

3. In a molding machine having a rotatable turret equipped with aplurality of molding units, each of said units including a pair ofcomplemental elements relatively movable into and out of moldingrelationship,

a cylinder having a piston therein connected with one of said elements,a single line of high pressure fluid entering said turret, a lowpressure accumulator within said turret, mechanism for controllingmovement of said piston including a valve having multiple passagewaystherein, one of said passageways, when said valve is actuated in onedirection, connecting the base of said cylinder with said accumulator,said one passageway permitting fluid, in relatively large volume, toeffect any desired extent of movement of said piston in a direction tobring said elements into approximate molding relationship, anotherofsaid passageways simultaneously connecting the base of said cylinderwith said high pressure fluid line to an extent to effect completemolding relationship of said elements, still another of saidpassageways, when said valve is actuated in the opposite direction,connecting the top of said cylinder with the high pressure fluid sourcewhereby to effect separation of said pair of elements, a further of saidpassageways connecting the base of said piston with the source of saidlow pressure fluid, and a safety valve consisting of a cylinder and apiston therein, connection of' said high pressure fluid with saidcylinder serving to hold said piston in a position to permit lowpressure fluid from said accumulator to pass through said safety valveto the first mentioned cylinder when said high pressure fluid is above agiven value.

4. In a molding machine having a rotatable turret equipped with aplurality of molding units, each of said units including a pair ofcomplemental elements relatively movable into and out of moldingrelationship, a cylinder having a piston therein connected with one ofsaid elements, a single line of high pressure fluid entering saidturret, a low pressure accumulator within said turret, mechanism forcontrolling movement of said piston iucluding a valve having multiplepassageways therein, one of said passageways, when said valve isactuated in one direction, connecting the base of said cylinder withsaid accumulator, said one passageway permitting fluid, in relativelylarge volume, to effect any desired extent of movement of said piston ina direction to bring said elements into approximate moldingrelationship, another of said passageways simultaneously connect-ing thebase of said cylinder with said high pressure fluid line to an extent toeffect complete molding relationship of said elements, still another ofsaid passageways, when said valve is actuated in the opposite direction,connecting the top of said cylinder with the high pressure fluid sourcewhereby to effect separation of said pair of elements, and a further ofsaid passageways connecting the base of said piston with the source ofsaid low pressure fluid, and other valve means in the high pressure lineoperable to prevent flow of fluid from said accumulator into saidcylinder when the pressure in said high pressure line drops below agiven value.

5. In a molding machine having a rotatable turret, a plurality ofmolding units disposed radially about said turret, hydraulicallyoperated mechanism for closing and opening the molding elements of eachof said units, an external source of high pressure fluid entering saidturret, an accumulator in said turret providing fluid under lowpressure, a cylinder having a piston therein joined to one of theelements of each of said units, a valve for each of said unitsinterposed between said cylinder and lines from said high pressuresource and said accumulator, a passageway in said valve providingcontinuous low pressure fluid to the base of said piston, means in saidvalve in one operative position connecting the base of said piston withsaid high pressure source, said means also serving to connect the top ofsaid piston with a fluid return line, said means, in another operativeposition, connecting the base of said piston with said accumulator andthe top of said piston with said high pressure source, and other meansenabling lluid from the base of said piston to by-pass said accumulatorand enter said fluid return line when pressure in said accumulatorattains a given value.

6. In a molding machine having a rotatable turret, a plurality ofmolding units disposed radially about said turret, hydraulicallyoperated mechanism for closing and opening the molding elements of eachof said units, an external source of high pressure fluid entering saidturret, an accumulator in said turret providing iluid under lowpressure, a cylinder having a piston therein joined to one of theelements of each of said units, a valve for each of said unitsinterposed between said cylinder and lines from said high pressuresource and said accumulator, said valve having two sets of passageways,one of said sets being connected with said cylinder, the other of saidsets being connected with said high pressure source and saidaccumulator, a rotatable shaft in said valve, said shaft having furtherpassageways for connecting certain passageways of said sets when saidshaft is rotated whereby to selectively present high pressure fluid tothe top and bottom of said piston and to at all times present lowpressure tluid from said accumulator to the bottom of said piston duringoperation of said machine, and other valve means in said high pressureline operable to prevent ow of fluid from said accumulator to saidcylinder when the pressure in said highV pressure line drops below agiven value.

7. In a molding machine having a rotatable turret, a plurality ofmolding units disposed radially about said turret, hydraulicallyoperated mechanism for closing and opening the molding elements of eachof said units, an external source of high pressure fluid entering saidturret, an accumulator in said turret providing uid under low pressure,a cylinder having a piston therein joined to one of the elements of eachof said units, a valve for each of said units interposed between saidcylinder and lines from said high pressure source and said accumulator,said valve having two sets of passageways, one of said sets beingconnected with Said cylinder, the other of said sets being connectedwith said high pressure source and said accumulator, a rotatable shaftin said valve, said shaft having further passageways for connectingcertain passageways of said sets when said shaft is rotated whereby toselectively present high pressure tluid to the top and bottom of saidpiston and to at all times present low pressure fiuid from saidaccumulator to the bottom of said piston, and other valve means in thehigh pressure line operable to prevent ow of fluid from the accumulatorinto said cylinder when the pressure in said high pressure line dropsbelow a given value.

References Cited in the tile of this patent UNITED STATES PATENTS2,155,316 Lauterbach Apr. 18, 1939 2,568,042 Vltavsky Sept. 18, 19512,728,946 Pinsenschaum Jan. 3, 1956 2,805,447 Voges Sept. l0, 1957

